Colorimetry Mn In Steel 1n4x1c

Colorimetric Determination of Manganese in Steel: Aim:- The aim of this experiment was to find out the percentage of manganese present in a steel paper clip. Introduction:Colorimetry is an analytical technique that is used to determine the concentrations of coloured substances in solution. It relies on the fact that a coloured substance absorbs light of a complimentary colour to its own and that the amount of light absorbs is proportional to its concentration. Colorimetry is particularly suited to the determination of manganese in steel because the manganese can be converted to the permanganate (VII) ion which is strongly coloured. The oxidation is achieved in two stages: 1st stage oxidation [IMAGE] Mn(s) Mn2+(aq) This oxidation is brought about by the nitric acid which itself is reduced to nitrogen monoxide, which forms nitrogen dioxide (brown fumes) on with the air. 2nd Oxidation [IMAGE]2 Mn2+(aq) + 5IO-4 + 3H2O 2MnO-4(aq) + 6H+ + 5IO3-(aq) The oxidation is bought about by Potassium Periodate. Procedure:Part-A Calibration Graph Standard solutions of acidified potassium permanganate solution were made up by diluting (2, 4, 6, 8, 10, 12, 14cm3) stock standard solution (of 9.78 x 10-4 moll-1) to the mark in a (50cm3) standard flask. Using a spectrophotometer the absorbance of each solution was measured in the colorimeter using deionised water as a standard in optically matched cuvettes. A calibration graph of absorbance against concentration of the potassium permanganate solution was plotted. Part-B Oxidation of Manganese to Permanganate The steel paper clip was degreased with propanone, dried, cut into small pieces and accurately weighed (approx 0.2g). The steel was then placed in a separate (250ml) tall form glass beaker. Nitric acid (approx 40ml of 2M) was added to the beaker and heated gently to dissolve the steel. The mixture was heated cautiously, in a fume cupboard, until the reaction began. Once the steel was dissolved (after about 10 minutes), the solution was cooled a little. A glass rod was placed in the beaker and then the solution was boiled until no more brown fumes were given off (after about 10 minutes). The solution was cooled considerably; the glass on the top was carefully removed and the underside was washed into the beaker. Phosphoric acid (approx 5ml of 85%) was added while stirring and then potassium persulphate

(approximately 0.2g) was added. To this solution (20ml of 2M) nitric acid containing potassium periodate (approx 1g) was added and the mixture was gently brought to boiling. The solution started to turn pink. Once the intensity of pink colour remained constant the heating was stopped. The solution was allowed to cool overnight at room temperature. The solution was then transferred to a standard flask (100ml) and distilled water added up to the mark. The flask was inverted several times to mix the contents well. The absorbance was measured in a spectrophotometer at a wavelength of 525 nm. The calibration curve was used to convert the absorbance to a permanganate concentration and from that; the percentage of manganese in the steel paper clip could be calculated. Hazcon:* Wear eye protection and if any chemical splashes on your skin wash it off immediately. * The acidified potassium permanganate is harmful if ingested and irritates the eyes and skin. * Both 2M nitric acid and its vapour are corrosive and toxic causing severe burns to the eyes, digestive and respiratory systems and in with the skin. * 85% phosphoric acid is corrosive, it burns Results:1. Table Volume of stock solution in 50ml Absorbance 2 0.074 4 0.155 6 0.245 8 0.330 10 0.405 12 0.490 14

0.561 2. Calibration Curve [IMAGE] Mass of Clip1:- 0.280g Absorbance of solution from Clip1:- 0.35 = 9ml of stock solution per 50ml Mass of Clip2:- 0.265g Absorbance of solution from Clip2:- 0.26 = 6.2ml of stock solution per 50ml Method-1 Absorbance = 0.35 = 9ml of stock solution per 50ml Concentration of MnO4- = (9.78 x 10-4) x 9/50 = 1.76 x 10-4 mol/l Moles of MnO4- in sample of 100ml = 1.76 x 10-4 x 0.1 = 1.76 x 10-5 mol Moles of MnO4- = Moles of Mn 1.76 x10-5 1.76 x 10-5 Mass of Mn = moles x gFm = (91.76 x 10-5) x 54.9 = 9.66 x 10-4 g % of Mn = 9.66 x 10-4 /0.280 x 100 = 0.345% Method-2 Absorbance = 0.26 = 6.2ml of stock solution per 50ml Concentration of MnO4- = (9.78 x 10-4) x 6.2/50 = 1.21 x 10-4 mol/l Moles of MnO4- in sample of 100ml = 1.21 x 10-4 x 0.1 = 1.21 x 10-5 mol Moles of MnO4- = Moles of Mn 1.21 x 10-5 1.21 x 10-5

Mass of Mn = moles x gFm = 1.21 x 10-5 x 54.9 = 6.64 x 10-4 g % of Mn = 6.64 x 10-4 /0.280 x 100 = 0.237% Conclusion:The percentage of Mn in steel is 0.345% and 0.237 %. Discussion:The wavelength was set at 525nm 1nm and it only allowed light of that wavelength. Optically matched cuvettes were used so that any light distortion is cancelled out. A calibration curve was prepared to compare absorbance of a solution of unknown concentration to that of a solution of known concentration the unknown concentration to be determined. . ========================= Analytica Chimica Acta Volume 2, February 1948, Pages 377-396 The colorimetric determination of nickel, chromium, and manganese in steel Purchase the full-text article H.A.J. Pietersa, W.J. Hanssena and J.J. Geurtsa a Central Laboratory of the Netherlands State Coal Mines, GeleenNetherlands Received 18 March 1948. Available online 22 January 2002. Abstract With the aid of the Spckkei absorptiometer the colonmetnc delerminations, of nic kel (with dimethylglyoxime), chromium (with diphenylcarbazide) and manganese (af ter oxidation with periodate) in steel were critically sinveyed The following fa ctors were examined. wave length of the light, concentration of the reagents, st ability of the coloured solution, temperature, influence of excess non, relation of extinetion coefficient and concentration of the coloured solution, influence of Mo, V, W, Ti, Al, Co, Cu, Ni, Cr, Mn, P and Si. For each determination a recommended procedure is given, with the results of con trol analyses. The recommended procedures are rapid. They can be used with steel s of widely differing composition. The methods are accurate within 5% of the act ual Value. 1. Nickle After neutrahsing the solution 5 ml (01 more) of concentrared ammonia (0.95) mus t be added. The temperature of the solution must be kept below 30° C before adding the dimethylglyoxime. The extinction coefficient is determined with light of 520 m/gm 2. Chromium The chromium is oxidised with hydrogen peroxide in alkaline solution. The influe nce of iron is ehminated by the addition of phosphoric acid. The recommended aci dity is o.2 n, the quantily of diphenylcarbazide is 2 ml of a 1%'s solution in a

ceton. The determinations are made with a mercury lamp and filter (546 m/gm) 3. Manganese The solution of the sampie is boiled with ammoniumpersulphate and then oxidised with 300 500 mg of potassium periodate. The recommended acidity is 2 n, using a mixture of equal parts of sulphuric and phosphoric acids. The determinations are made with light of 520 m/gm.

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here's a preview of the first 150 words of this essay with formatting removed fo r you to read Have a little read: ... A Colorimetric Determination of Manganese In Steel Advan ced Higher Chemistry Unit 1 PPA 2 Eilidh L Hawkins Candidate Number 972840254 Th e aim of this investigation is to determine the percentage Manganese in steel th rough colorimetric determination. Colorimetry is used to determine the concentra tions of coloured substances in solution. It works on the basis that a coloured substance absorbs light of a colour complementary to its own and also that the a mount of light absorbed (absorbance) is proportional to the substance's concentr ation. This technique is especially suited to determining the percentage mangane se in steel because manganese can be converted into permanganate ions. Permangan ate ions are coloured. There are two stages in the conversion: the first uses ni tric acid to oxidise manganese to manganese (II) ions. Mn(s) Mn2+(aq) + 2e The m anganese (II) ions are then oxidised to permanganate ions by potassium periodate . Mn2+(aq) + 4H2O MnO4-(aq) + 8H+ + 5e To find the filter which gives maximum ab sorbance. A burette was rinsed and

here's a preview of the first 150 words of this essay with formatting removed fo r you to read Have a little read: ... Spectrophotometric Determination of Manganese in Steel I ntroduction The aim of this experiment was to determine the average percentage c oncentration of manganese in steel. This is useful when it is necessary to deter mine the strength of the steel. Spectrophotometric analysis was used in this exp eriment. This is a technique that can be successfully used to determine the conc entrations of coloured substances in solution. It works on the basis that a colo ured substance absorbs light of a colour complementary to its own and also that the amount of light absorbed is proportional to the substance's concentration.Sp ectrophotometric analysis was relevant in this experiment because the permangana te ions that are formed from the manganese were coloured, allowing spectrophotom

etry to be used to work out the absorbance by absorbing all the other colours ot her than the colour of the permanganate ions. The conversion of the manganese in to permanganate ions took place in two stages. Firstly, the manganese was oxidis ed here's a preview of the first 150 words of this essay with formatting removed fo r you to read Have a little read: ... Colorimetric Determination of Manganese in Steel Aim:- T he aim of this experiment was to find out the percentage of manganese present in a steel paper clip. Introduction:- Colorimetry is an analytical technique that is used to determine the concentrations of coloured substances in solution. It r elies on the fact that a coloured substance absorbs light of a complimentary col our to its own and that the amount of light absorbs is proportional to its conce ntration. Colorimetry is particularly suited to the determination of manganese i n steel because the manganese can be converted to the permanganate (VII) ion whi ch is strongly coloured. The oxidation is achieved in two stages: 1st stage oxid ation Mn(s) Mn2+(aq) This oxidation is brought about by the nitric acid which it self is reduced to nitrogen monoxide, which forms nitrogen dioxide (brown fumes) on with the air. 2nd Oxidation 2 Mn2+(aq) + 5IO-4 + 3H2O 2MnO-4(aq) + 6 H+ + 5IO3-(aq) The oxidation is bought about by